Memory cell biasing techniques during a read operation

ABSTRACT

Methods, systems, and devices for biasing a memory cell during a read operation are described. For example, a memory device may bias a memory cell to a first voltage (e.g., a read voltage) during an activation phase of a read operation. After biasing the memory cell to the first voltage, the memory device may bias the memory cell to a second voltage greater than the first voltage (e.g., a write voltage) during the activation phase of the read operation. After biasing the memory cell to the second voltage, the memory device may initiate a refresh phase of the read operation. Based on a value stored by the memory cell prior to biasing the memory cell to the first voltage, the memory device may initiate a precharge phase of the read operation.

CROSS REFERENCE

The present application for patent is a continuation of U.S. patentapplication Ser. No. 16/834,941 by Locatelli et al., entitled “MEMORYCELL BIASING TECHNIQUES DURING A READ OPERATION,” filed Mar. 30, 2020,assigned to the assignee hereof, and is expressly incorporated byreference in its entirety herein.

BACKGROUND

The following relates generally to a system that includes at least onememory device and more specifically to memory cell biasing techniquesduring a read operation.

Memory devices are widely used to store information in variouselectronic devices such as computers, wireless communication devices,cameras, digital displays, and the like. Information is stored byprogramming memory cells within a memory device to various states. Forexample, binary memory cells may be programmed to one of two supportedstates, often denoted by a logic 1 or a logic 0. In some examples, asingle memory cell may support more than two states, any one of whichmay be stored. To access the stored information, a component of thedevice may read, or sense, at least one stored state in the memorydevice. To store information, a component of the device may write, orprogram, the state in the memory device.

Various types of memory devices exist, including magnetic hard disks,random access memory (RAM), read-only memory (ROM), dynamic RAM (DRAM),synchronous dynamic RAM (SDRAM), ferroelectric RAM (FeRAM), magnetic RAM(MRAM), resistive RAM (RRAM), flash memory, phase change memory (PCM),and others. Memory devices may be volatile or non-volatile. Non-volatilememory, e.g., FeRAM, may maintain their stored logic state for extendedperiods of time even in the absence of an external power source.Volatile memory devices, e.g., DRAM, may lose their stored state whendisconnected from an external power source. FeRAM may be able to achievedensities similar to volatile memory but may have non-volatileproperties due to the use of a ferroelectric capacitor as a storagedevice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a memory device that supports memorycell biasing techniques during a read operation in accordance withexamples as disclosed herein.

FIG. 2 illustrates an example of a circuit that supports memory cellbiasing techniques during a read operation in accordance with examplesas disclosed herein.

FIGS. 3A and 3B illustrate examples of non-linear electrical propertiesof a ferroelectric memory cell in accordance with examples as disclosedherein.

FIG. 4 illustrates a timing diagram that supports memory cell biasingtechniques during a read operation in accordance with examples asdisclosed herein.

FIG. 5 illustrates an example of a circuit that supports memory cellbiasing techniques during a read operation in accordance with examplesas disclosed herein.

FIG. 6 illustrates an example voltage plot for a memory cell thatsupports memory cell biasing techniques during a read operation inaccordance with examples as disclosed herein.

FIG. 7 shows a block diagram of a memory device that supports memorycell biasing techniques during a read operation in accordance withexamples as disclosed herein.

FIG. 8 shows a flowchart illustrating a method or methods that supportmemory cell biasing techniques during a read operation in accordancewith examples as disclosed herein.

DETAILED DESCRIPTION

Memory devices may use various sensing operations to determine a logicstate stored by a memory cell of a memory array. The memory device mayapply one or more voltages to the memory cell to execute the varioussensing or read operations. For example, the memory device may apply oneor more voltages to the memory cell during an activation phase of theread operation. The memory device may subsequently apply one or moreadditional voltages to the memory cell during a refresh phase of thememory operation. Additionally, the memory device may apply one or morevoltages to the memory cell during a precharge phase of the readoperation. In some cases, the memory device may apply relatively highvoltages to the memory cell when performing a read operation. Readingmemory cells using high voltages may cause parasitic effects such aslarger leakage currents. In turn, these effects may cause disturbanceson memory cells in the memory array thereby decreasing functionality andreliability when reading memory cells. In some cases, reducing thevoltage level of the one or more voltages applied to the memory cellduring a sensing operation may improve a performance of the memorydevice.

In accordance with examples as disclosed herein, a memory device mayreduce a voltage applied to the memory cell during the activation phaseof the read operation. Some memory devices may bias the memory cell to awrite voltage during the activation phase of the read operation. Amemory device may reduce the voltage applied to the memory cell during afirst portion of the activation phase to a read voltage that is lessthan the write voltage, as compared with other read operations. Forexample, during the activation phase the memory device may first biasthe memory cell to a first voltage (e.g., a read voltage) to determine alogic state stored by the memory cell. The memory device maysubsequently increase the voltage bias of the memory cell to a secondvoltage (e.g., a write voltage) during the activation phase of the readoperation. In some cases, reducing the voltage level applied to thememory cell during the activation phase of the read operation maymaintain a performance of the read operation while reducing thedisturbances on other memory cells caused by the read operation.

Features of the disclosure are initially described in the context of amemory device and related circuitry as described with reference to FIGS.1 and 2. Features of the disclosure are described in the context memorycell characteristics, and associated circuits, and timing diagrams, asdescribed with reference to as described with reference to FIGS. 3-6.These and other features of the disclosure are further illustrated byand described with reference to an apparatus diagram and a flowchartthat relate to memory cell biasing techniques during a read operation asdescribed with reference to FIGS. 7 and 8.

FIG. 1 illustrates an example of a memory device 100 that supportsdifferential sensing for a memory device in accordance with examples asdisclosed herein. The memory device 100 may also be referred to as anelectronic memory apparatus. The memory device 100 may include memorycells 105 that are programmable to store different logic states. In somecases, a memory cell 105 may be programmable to store two logic states,denoted a logic 0 and a logic 1. In some cases, a memory cell 105 may beprogrammable to store more than two logic states (e.g., as a multi-levelcell (MLC)). The set of memory cells 105 may be part of a memory section110 of the memory device 100 (e.g., including an array of memory cells105), where, in some examples, a memory section 110 may refer to acontiguous tile of memory cells 105 (e.g., a contiguous set of elementsof a semiconductor chip).

In some examples, a memory cell 105 may store an electric chargerepresentative of the programmable logic states (e.g., storing charge ina capacitor, capacitive memory element, capacitive storage element). Inone example, a charged and uncharged capacitor may represent two logicstates, respectively. In another example, a positively charged (e.g., afirst polarity, a positive polarity) and negatively charged (e.g., asecond polarity, a negative polarity) capacitor may represent two logicstates, respectively. DRAM or FeRAM architectures may use such designs,and the capacitor employed may include a dielectric material with linearor para-electric polarization properties as an insulator. In someexamples, different levels of charge of a capacitor may representdifferent logic states, which, in some examples, may support more thantwo logic states in a respective memory cell 105. In some examples, suchas FeRAM architectures, a memory cell 105 may include a ferroelectriccapacitor having a ferroelectric material as an insulating (e.g.,non-conductive) material between terminals of the capacitor. Differentlevels or polarities of polarization of a ferroelectric capacitor mayrepresent different logic states (e.g., supporting two or more logicstates in a respective memory cell 105).

In the example of memory device 100, each row of memory cells 105 may becoupled with one of a set of first access lines 120 (e.g., a word line(WL), such as one of WL₁ through WL_(M)), and each column of memorycells 105 may be coupled with one of a set of second access lines 130(e.g., a digit line (DL), such as one of DL₁ through DL_(N)). Ingeneral, one memory cell 105 may be located at the intersection of(e.g., coupled with, coupled between) an access line 120 and an accessline 130. This intersection may be referred to as an address of a memorycell 105. A target or selected memory cell 105 may be a memory cell 105located at the intersection of an energized or otherwise selected accessline 120 and an energized or otherwise selected access line 130.

In some architectures, a storage component of a memory cell 105 may beelectrically isolated (e.g., selectively isolated) from a second accessline 130 by a cell selection component, which, in some examples, may bereferred to as a switching component or a selector device of orotherwise associated with the memory cell 105. A first access line 120may be coupled with the cell selection component (e.g., via a controlnode or terminal of the cell selection component), and may control thecell selection component of the memory cell 105. For example, the cellselection component may be a transistor and the first access line 120may be coupled with a gate of the transistor (e.g., where a gate node ofthe transistor may be a control node of the transistor). Activating afirst access line 120 may result in an electrical connection or closedcircuit between a respective logic storing component of one or morememory cells 105 and one or more corresponding second access lines 130.A second access line 130 may then be accessed to read from or write tothe respective memory cell 105.

In some examples, memory cells 105 may also be coupled with one of aplurality of third access lines 140 (e.g., a plate line (PL), such asone of PL₁ through PL_(N)). In some examples, each of the third accesslines 140 may be independently addressable (e.g., supporting individualselection or biasing). In some examples, the plurality of third accesslines 140 may represent or be otherwise functionally equivalent with acommon plate, or other common node (e.g., a plate node common to each ofthe memory cells 105 in the memory section 110). When a memory cell 105employs a capacitor for storing a logic state, a second access line 130may provide access to a first terminal or a first plate of thecapacitor, and a third access line 140 may provide access to a secondterminal or a second plate of the capacitor. Although the plurality ofthird access lines 140 of the memory device 100 are shown assubstantially parallel with the plurality of second access lines 130, inother examples, a plurality of third access lines 140 may besubstantially parallel with the plurality of first access lines 120, orin any other configuration (e.g., a common planar conductor, a commonplate material).

Access operations such as reading, writing, rewriting, and refreshingmay be performed on a memory cell 105 by activating or selecting a firstaccess line 120, a second access line 130, or a third access line 140coupled with the memory cell 105, which may include applying a voltage,a charge, or a current to the respective access line. Upon selecting amemory cell 105 (e.g., in a read operation), a resulting signal may beused to determine the logic state stored by the memory cell 105. Forexample, a memory cell 105 with a capacitive memory element storing alogic state may be selected, and the resulting flow of charge via anaccess line or resulting voltage of an access line may be detected todetermine the programmed logic state stored by the memory cell 105.Access lines 120, 130, and 140 may be made of conductive materials, suchas metals (e.g., copper (Cu), silver (Ag), aluminum (Al), gold (Au),tungsten (W), titanium (Ti)), metal alloys, carbon, or other conductiveor semi-conductive materials, alloys, or compounds.

Accessing memory cells 105 may be controlled through a row component 125(e.g., a row decoder), a column component 135 (e.g., a column decoder),or a plate component 145 (e.g., a plate decoder, a plate driver), or acombination thereof. For example, a row component 125 may receive a rowaddress from the memory controller 170 and activate the appropriatefirst access line 120 based on the received row address. Similarly, acolumn component 135 may receive a column address from the memorycontroller 170 and activate the appropriate second access line 130. Insome examples, such access operations may be accompanied by a platecomponent 145 biasing one or more of the third access lines 140 (e.g.,biasing one of the third access lines 140, biasing the third accesslines 140, biasing a common plate).

In some examples, the memory controller 170 may control operations(e.g., read operations, write operations, rewrite operations, refreshoperations) of memory cells 105 through the various components (e.g.,row component 125, column component 135, plate component 145, sensecomponent 150). In some cases, one or more of the row component 125, thecolumn component 135, the plate component 145, and the sense component150 may be co-located or otherwise included with the memory controller170. The memory controller 170 may generate row and column addresssignals to activate a desired access line 120 and access line 130. Thememory controller 170 may also generate or control various voltages orcurrents used during the operation of memory device 100.

In various examples, one, multiple, or all memory cells 105 withinmemory device 100 may be accessed simultaneously. For example, each ofthe memory cells 105 that share a common access line 120, or some subsetof the memory cells 105 that share a common access line 120 (e.g., acommon cell selection line), may be accessed simultaneously (e.g.,according to a memory row access arrangement, according to a “page”access arrangement, according to a set of access lines 130 or columnsthat may be accessed or sensed simultaneously). In another example,multiple or all memory cells 105 of memory device 100 may be accessedsimultaneously during a reset operation in which memory cells 105, or agroup of memory cells 105 (e.g., the memory cells 105 of a memorysection 110), are set to a single logic state.

A memory cell 105 may be read (e.g., sensed) by a sense component 150when the memory cell 105 is accessed (e.g., in cooperation with thememory controller 170) to determine a logic state written to or storedby the memory cell 105. For example, during an activation phase of aread operation the sense component 150 may be configured to evaluate acurrent or charge transfer through or from the memory cell 105, or avoltage resulting from coupling the memory cell 105 with the sensecomponent 150, responsive to a read operation. The sense component 150may provide an output signal indicative of the logic state read from thememory cell 105 to one or more components (e.g., to the column component135, the input/output component 160, to the memory controller 170).

A sense component 150 may include various switching components,selection components, transistors, amplifiers, capacitors, resistors, orvoltage sources to detect or amplify a difference in sensing signals(e.g., a difference between a read voltage and a reference voltage, adifference between a read current and a reference current, a differencebetween a read charge and a reference charge), which, in some examples,may be referred to as latching. In some examples, a sense component 150may include a collection of components (e.g., circuit elements) that arerepeated for each of a set of access lines 130 connected to the sensecomponent 150. For example, a sense component 150 may include a separatesensing circuit (e.g., a separate or duplicated sense amplifier, aseparate or duplicated signal development component) for each of a setof access lines 130 coupled with the sense component 150, such that alogic state may be separately detected for a respective memory cell 105coupled with a respective one of the set of access lines 130.

During the activation phase of the read operation, the memory controller170 may bias a memory cell 105 (e.g., a target memory cell 105 to beread during an execution of the read operation) by applying one or morevoltages to the memory cell 105. For example, the row component 125 maybias an access line 120 (e.g., WL1) to a first voltage (e.g., a readvoltage). While the memory cell is biased to the first voltage, thesense component 150 may be configured to evaluate an amount of chargestored in the memory cell 105 (e.g., based on a logic value stored bythe memory cell 105). After biasing the memory cell 105 to the firstvoltage, the row component 125 may bias the memory cell 105 to a secondvoltage greater than the first voltage (e.g., a write voltage) duringthe activation phase of the read operation. The second voltage may beapproximately equal to a saturation voltage associated with the memorycell 105. That is, biasing the memory cell 105 to the second voltage maycause the memory cell 105 to saturate or be associated with a saturatedcharge capacity.

In some memory architectures, accessing a memory cell 105 may degrade ordestroy a stored logic state, and rewrite or refresh operations may beperformed to return the stored logic state to memory cell 105 (e.g.,during a refresh phase and/or a precharge phase of the read operation).In DRAM or FeRAM, for example, a capacitor of a memory cell 105 may bepartially or completely discharged or depolarized during a senseoperation, thereby corrupting the logic state that was stored in thememory cell 105. Thus, in some examples, the logic state stored in amemory cell 105 may be rewritten after an access operation. Further,activating a single access line 120, 130, or 140 may result in thedischarge of memory cells 105 coupled with the activated access line120, 130, or 140. Thus, one or more memory cells 105 coupled with anaccess line 120, 130, or 140 associated with an access operation (e.g.,cells of an accessed row, cells of an accessed column) may be rewrittenafter an access operation.

In some examples, reading a memory cell 105 may be non-destructive. Thatis, the logic state of the memory cell 105 may not be rewritten afterthe memory cell 105 is read. However, in some examples, refreshing thelogic state of the memory cell 105 may or may not be needed in theabsence or presence of other access operations. For example, the logicstate stored by a memory cell 105 may be refreshed at periodic intervalsby applying an appropriate write, rewrite, or refresh bias to maintainthe stored logic state.

A memory cell 105 may be set, or written, by activating the relevantfirst access line 120, second access line 130, or third access line 140(e.g., via a memory controller 170). In other words, a logic state maybe stored in a memory cell 105. Row component 125, column component 135,or plate component 145 may accept data, for example, via input/outputcomponent 160, to be written to the memory cells 105. In some examples,a write operation may be performed at least in part by a sense component150, or a write operation may be configured to bypass a sense component150.

In the case of a capacitive memory element, a memory cell 105 may bewritten by applying a voltage to or across a capacitor, and thenisolating the capacitor (e.g., isolating the capacitor from a voltagesource used to write the memory cell 105, floating the capacitor) tostore a charge in the capacitor associated with a desired logic state.In the case of ferroelectric memory, a ferroelectric memory element(e.g., a ferroelectric capacitor) of a memory cell 105 may be written byapplying a voltage with a magnitude high enough to polarize theferroelectric memory element (e.g., applying a saturation voltage) witha polarization associated with a desired logic state, and theferroelectric memory element may be isolated (e.g., floating), or a zeronet voltage or bias may be applied across the ferroelectric memoryelement (e.g., grounding, virtually grounding, or equalizing a voltageacross the ferroelectric memory element).

FIG. 2 illustrates an example circuit 200 that supports differentialsensing for a memory device in accordance with examples as disclosedherein. Circuit 200 includes a memory cell 105-a and a sense component150-a, which may be examples of the respective components as describedwith reference to FIG. 1. Circuit 200 also includes a word line 205, adigit line 210, and a plate line 215, which, in some examples, maycorrespond to a first access line 120, a second access line 130, and athird access line 140, respectively (e.g., of a memory section 110), asdescribed with reference to FIG. 1. In various examples, the plate line215 may be illustrative of an independently-addressable plate line, or acommon plate node (e.g., or a memory section 110 that includes thememory cell 105-a).

The memory cell 105-a may include a logic storage component (e.g., amemory element, a storage element, a memory storage element), such as acapacitor 220 that has a first plate, cell plate 221, and a secondplate, cell bottom 222. The cell plate 221 and the cell bottom 222 maybe capacitively coupled through a dielectric material positioned betweenthem (e.g., in a DRAM application), or capacitively coupled through aferroelectric material positioned between them (e.g., in a FeRAMapplication). The cell plate 221 may be associated with a voltageV_(plate), and cell bottom 222 may be associated with a voltageV_(bottom), as illustrated in the circuit 200. The cell plate 221 may beaccessed via the plate line 215 and cell bottom 222 may be accessed viathe digit line 210. As described herein, various logic states may bestored by charging, discharging, or polarizing the capacitor 220.

The capacitor 220 may be electrically connected to the digit line 210,and the stored logic state of the capacitor 220 may be read or sensed byoperating various elements represented in circuit 200. For example, thememory cell 105-a may also include a cell selection component 230 which,in some examples, may be referred to as a switching component or aselector device coupled with or between an access line (e.g., the digitline 210) and the capacitor 220. In some examples, a cell selectioncomponent 230 may be considered to be outside the illustrative boundaryof the memory cell 105-a, and the cell selection component 230 may bereferred to as a switching component or selector device coupled with orbetween an access line (e.g., the digit line 210) and the memory cell105-a.

The capacitor 220 may be selectively coupled with the digit line 210when the cell selection component 230 is activated (e.g., by way of anactivating logical signal), and the capacitor 220 can be selectivelyisolated from the digit line 210 when the cell selection component 230is deactivated (e.g., by way of a deactivating logical signal). Alogical signal or other selection signal or voltage may be applied to acontrol node 235 of the cell selection component 230 (e.g., via the wordline 205). In other words, the cell selection component 230 may beconfigured to selectively couple or decouple the capacitor 220 and thedigit line 210 based on a logical signal or voltage applied via the wordline 205 to the control node 235.

Activating the cell selection component 230 may be referred to asselecting or activating the memory cell 105-a, and deactivating the cellselection component 230 may be referred to as deselecting ordeactivating the memory cell 105-a. In some examples, the cell selectioncomponent 230 is a transistor and its operation may be controlled byapplying an activation voltage to the transistor gate (e.g., a controlor selection node or terminal). The voltage for activating thetransistor (e.g., the voltage between the transistor gate terminal andthe transistor source terminal) may be a voltage greater than thethreshold voltage magnitude of the transistor. In some examples,activating the cell selection component 230 may be referred to asselectively coupling the memory cell 105-a with the digit line 210.

Biasing the plate line 215 or the digit line 210 may result in a voltagedifference (e.g., the voltage of the digit line 210 minus the voltage ofthe plate line 215) across the capacitor 220. The voltage difference mayaccompany a change in the charge stored by the capacitor 220 (e.g., dueto charge sharing between the capacitor 220 and the digit line 210, dueto charge sharing between the capacitor 220 and the plate line 215), andthe magnitude of the change in stored charge may depend on the initialstate of the capacitor 220 (e.g., whether the initial charge or logicstate stored a logic 1 or a logic 0).

To perform a read operation on the memory cell 105-a, a first voltagemay be applied across the capacitor 220 during an activation phase ofthe read operation by increasing the voltage of the digit line 210 andholding a voltage of the plate line 215 to a constant voltage (e.g.,approximately 0 volts). While the capacitor 220 is biased to the firstvoltage, charge may flow into or out of the capacitor 220. After biasingthe memory cell 105-a to the first voltage, the voltage of the digitline 210 may be increased to a second voltage to bias the capacitor 220to the second voltage (e.g., a write voltage) during the activationphase of the read operation. Biasing the capacitor 220 to the secondvoltage may cause the capacitor 220 to saturate (e.g., be associatedwith a saturated charge capacity).

The digit line 210 may be coupled with additional memory cells 105 (notshown), and the digit line 210 may have properties that result in anon-negligible intrinsic capacitance 240 (e.g., on the order ofpicofarads (pF)), which may couple the digit line 210 with a voltagesource 250-a. The voltage source 250-a may represent a common ground orvirtual ground voltage, or the voltage of an adjacent access line of thecircuit 200 (not shown). Although illustrated as a separate element inFIG. 2, the intrinsic capacitance 240 may be associated with propertiesdistributed throughout the digit line 210.

The sense component 150-a may include a signal development component 260and a sense amplifier 270 coupled with the signal development component260 via a signal line 265. In various examples, the signal developmentcomponent 260 may include circuitry configured to amplify or otherwiseconvert signals of the digit line 210 prior to a logic state detectionoperation (e.g., by the sense amplifier 270). The signal developmentcomponent 260 may include, for example, a transistor, an amplifier, acascode, or any other circuitry configured to develop a signal forsensing a logic state stored by the memory cell 105-a. In some examples,the signal development component 260 may include a charge transfersensing amplifier (CTSA), which may include one or more transistors in acascode or voltage control configuration.

Although the digit line 210 and the signal line 265 are identified asseparate lines, the digit line 210, the signal line 265, and any otherlines connecting a memory cell 105 with a sense amplifier 270 may bereferred to as a single access line (e.g., of or associated with thememory cell 105). Constituent portions of such an access line may beidentified separately for the purposes of illustrating interveningcomponents and intervening signals in various example configurations.

The sense amplifier 270 may include a first node 291 and a second node292 which, in some examples, may be coupled with different access linesof a circuit (e.g., a signal line 265 and a reference line 285 of thecircuit 200, respectively) or, in other examples, may be coupled with acommon access line of a different circuit (not shown). In some examples,the first node 291 may be referred to as a signal node, and the secondnode 292 may be referred to as a reference node. However, otherconfigurations of access lines or reference lines may be used to supportthe techniques described herein.

The sense amplifier 270 may include various transistors or amplifiers todetect, convert, or amplify a difference in signals, which may bereferred to as latching. For example, the sense amplifier 270 mayinclude circuit elements that receive and compare a sense signal voltage(e.g., V_(sig), of the signal line 265) at a first node 291 with areference signal voltage (e.g., V_(ref), of a reference line 285) at asecond node 292. A voltage of the first node 271 may be based onaccessing the memory cell 105-a, such as a voltage based at least inpart on a charge transfer of the capacitor 220 while the cell selectioncomponent 230 is activated. In some examples, a voltage of the secondnode 292 may be provided by a reference component 280. In otherexamples, the reference component 280 may be omitted and a referencevoltage may be provided, for example, by accessing the memory cell 105-ato generate the reference voltage (e.g., in a self-referencing accessoperation). An output of the sense amplifier 270 may be driven to arelatively higher voltage (e.g., a positive voltage) or a relativelylower voltage (e.g., a negative voltage, a ground voltage) based on thecomparison at the sense amplifier 270.

The sense amplifier 270 may output a detected logic state via one ormore I/O lines 275 based on a comparison of signals at the first node271 and the second node 272. For example, if the first node 271 has alower voltage than the second node 272, an output of the sense amplifier270 may be driven to a relatively lower voltage of a first senseamplifier voltage source 250-b (e.g., a voltage of VL, which may be aground voltage substantially equal to V₀ or a negative voltage). If thefirst node 271 has a higher voltage than the second node 272, an outputof the sense amplifier 270 may be driven to the voltage of a secondsense amplifier voltage source 250-c (e.g., a voltage of V_(H)). Thesense component 150-a may latch the output of the sense amplifier 270 todetermine the logic state stored in the memory cell 105-a (e.g.,latching or determining a logic 0 when the first node 271 has a lowervoltage than the second node 272, latching or determining a logic 1 whenthe first node 271 has a higher voltage than the second node 272). Thelatched output of the sense amplifier 270, corresponding to the detectedlogic state of memory cell 105-a, may be output via one or moreinput/output (I/O) lines (e.g., I/O line 275), which may include anoutput through a column component 135 or an input/output component 160described with reference to FIG. 1.

To perform a write operation on the memory cell 105-a, a voltage may beapplied across the capacitor 220 by controlling the voltage of the cellplate 221 (e.g., through the plate line 215) and the cell bottom 222(e.g., through the digit line 210). For example, to write a logic 0, thecell plate 221 may be taken low (e.g., grounding the plate line 215,virtually grounding the plate line 215, applying a negative voltage tothe plate line 215), and the cell bottom 222 may be taken high (e.g.,applying a positive voltage to the digit line 210). The opposite processmay be performed to write a logic 1, where the cell plate 221 is takenhigh and the cell bottom 222 is taken low. In some cases, the voltageapplied across the capacitor 220 during a write operation may have amagnitude equal to or greater than a saturation voltage of aferroelectric material in the capacitor 220, such that the capacitor 220is polarized, and thus maintains a charge even when the magnitude ofapplied voltage is reduced, or if a zero net voltage is applied acrossthe capacitor 220.

The circuit 200, including the sense amplifier 270, the cell selectioncomponent 230, the signal development component 260, or the referencecomponent 280, may include various types of transistors. For example,the circuit 200 may include n-type transistors, where applying arelative positive voltage to the gate of the n-type transistor that isabove a threshold voltage for the n-type transistor (e.g., an appliedvoltage having a positive magnitude, relative to a source terminal, thatis greater than a threshold voltage) enables a conductive path betweenthe other terminals of the n-type transistor (e.g., a drain terminal andthe source terminal, across a conduction channel).

In some examples, the n-type transistor may act as a switchingcomponent, where the applied voltage is a logical signal that is used toenable conductivity through the transistor by applying a relatively highlogical signal voltage (e.g., a voltage corresponding to a logic 1state, which may be associated with a positive logical signal voltagesupply), or to disable conductivity through the transistor by applying arelatively low logical signal voltage (e.g., a voltage corresponding toa logic 0 state, which may be associated with a ground or virtual groundvoltage). In some examples where a n-type transistor is employed as aswitching component, the voltage of a logical signal applied to the gateterminal may be selected to operate the transistor at a particularworking point (e.g., in a saturation region or in an active region).

In some examples, the behavior of a n-type transistor may be morecomplex than a logical switching, and selective conductivity across thetransistor may also be a function of varying drain and source voltages.For example, the applied voltage at the gate terminal may have aparticular voltage level (e.g., a clamping voltage) that is used toenable conductivity between the drain terminal and the source terminalwhen the source terminal voltage is below a certain level (e.g., belowthe gate terminal voltage minus the threshold voltage). When the voltageof the source terminal rises above the certain level, the n-typetransistor may be deactivated such that the conductive path between thedrain terminal and source terminal is opened.

Additionally or alternatively, the circuit 200 may include p-typetransistors, where applying a relative negative voltage to the gate ofthe p-type transistor that is above a threshold voltage for the p-typetransistor (e.g., an applied voltage having a negative magnitude,relative to a source terminal, that is greater than a threshold voltage)enables a conductive path between the other terminals of the p-typetransistor (e.g., a drain terminal and the source terminal, across aconductive channel).

In some examples, the p-type transistor may act as a switchingcomponent, where the applied voltage is a logical signal that is used toenable conductivity by applying a relatively low logical signal voltage(e.g., a voltage corresponding to a logical “1” state, which may beassociated with a negative logical signal voltage supply), or to disableconductivity by applying a relatively high logical signal voltage (e.g.,a voltage corresponding to a logical “0” state, which may be associatedwith a ground or virtual ground voltage). In some examples where ap-type transistor is employed as a switching component, the voltage of alogical signal applied to the gate terminal may be selected to operatethe transistor at a particular working point (e.g., in a saturationregion or in an active region).

In some examples, the behavior of a p-type transistor may be morecomplex than a logical switching by the gate voltage, and selectiveconductivity across the transistor may also be a function of varyingdrain and source voltages. For example, the applied voltage at the gateterminal may have a particular voltage level that is used to enableconductivity between the drain terminal and the source terminal so longas the source terminal voltage is above a certain level (e.g., above thegate terminal voltage plus the threshold voltage). When the voltage ofthe source terminal voltage falls below the certain level, the p-typetransistor may be deactivated such that the conductive path between thedrain terminal and source terminal is opened.

A transistor of the circuit 200 may be a field-effect transistor (FET),including a metal oxide semiconductor FET, which may be referred to as aMOSFET. These, and other types of transistors may be formed by dopedregions of material on a substrate. In some examples, the transistor(s)may be formed on a substrate that is dedicated to a particular componentof the circuit 200 (e.g., a substrate for the sense amplifier 270, asubstrate for the signal development component 260, a substrate for thereference component 280, a substrate for the memory cell 105-a), or thetransistor(s) may be formed on a substrate that is common for particularcomponents of the circuit 200 (e.g., a substrate that is common to twoor more of the sense amplifier 270, the signal development component260, the reference component 280, or the memory cell 105-a). Some FETsmay have a metal portion including aluminum or other metal, but someFETs may implement other non-metal materials such as polycrystallinesilicon, including those FETs that may be referred to as a MOSFET.Further, although an oxide portion may be used as a dielectric portionof a FET, other non-oxide materials may be used in a dielectric materialin a FET, including those FETs that may be referred to as a MOSFET.

Although the circuit 200 illustrates a set of components relative to asingle memory cell 105, various components of the circuit 200 may beduplicated in a memory device 100 to support various operations. Forexample, to support row access or page access operations, a sensecomponent 150 may be configured with multiples of one or more of asignal development component 260, a signal line 265, a referencecomponent 280, a reference line 285, a sense amplifier 270, or othercomponents, where the multiples may be configured according to aquantity of memory cells 105 that may be accessed in a row access orpage access operation (e.g., in a concurrent operation). In variousexamples, a set of such multiples may correspond to or otherwise berepeated for each memory section 110 in a memory device 100, or such aset of multiples may be shared among one or more memory sections 110 ina memory device.

FIGS. 3A and 3B illustrate examples of non-linear electrical propertiesof a ferroelectric memory cell with hysteresis plots 300-a and 300-b,respectively, in accordance with various examples as disclosed herein.The hysteresis plots 300-a and 300-b may illustrate examples of variousphases within a read operation of a memory cell 105 employing aferroelectric capacitor 220 as described with reference to FIG. 2. Thehysteresis plots 300-a and 300-b depict the charge, Q, stored on aferroelectric capacitor 220 as a function of a voltage differenceV_(cap), between the terminals of the ferroelectric capacitor 220 (e.g.,when charge is permitted to flow into or out of the ferroelectriccapacitor 220 according to the voltage difference V_(cap)). For example,the voltage difference V_(cap) may represent the difference in voltagebetween a cell bottom 222 and a cell plate 221 (e.g.,V_(bottom)−V_(plate), V_(DL)−V_(PL)).

A ferroelectric material is characterized by an electric polarizationwhere the material may maintain a non-zero electric charge in theabsence of an electric field. Examples of ferroelectric materialsinclude barium titanate (BaTiO₃), lead titanate (PbTiO₃), lead zirconiumtitanate (PZT), and strontium bismuth tantalate (SBT). Ferroelectriccapacitors 220 described herein may include these or other ferroelectricmaterials. Electric polarization within a ferroelectric capacitor 220results in a net charge at the surface of the ferroelectric material,and attracts opposite charge through the terminals of the ferroelectriccapacitor 220. Thus, charge may be stored at the interface of theferroelectric material and the capacitor terminals.

FIG. 3A may include a hysteresis plot 300-a illustrating the process ofapplying a read voltage 315 to the memory cell during the activationphase of a read operation. As depicted in the hysteresis plot 300-a, aferroelectric material used in a ferroelectric capacitor 220 maymaintain a positive or negative polarization when there is no netvoltage difference between the terminals of the ferroelectric capacitor220. For example, the hysteresis plot 300-a illustrates two possiblepolarization states, a charge state 305-a and a charge state 310-a,which may represent a positively saturated polarization state and anegatively saturated polarization state, respectively. The charge states305-a and 310-a may be at a physical condition illustrating remnantpolarization (Pr) values, which may refer to the polarization (orcharge) that remains upon removing an external bias (e.g., voltage).According to the example of the hysteresis plot 300-a, the charge state305-a may represent a logic 0 when no voltage difference is appliedacross the ferroelectric capacitor 220, and the charge state 310-a mayrepresent a logic 1 when no voltage difference is applied across theferroelectric capacitor 220. In some examples, the logic values of therespective charge states or polarization states may be reversed orinterpreted in an opposite manner to accommodate other schemes foroperating a memory cell 105.

To read, or sense, the stored state of a ferroelectric capacitor 220, avoltage (e.g., a read voltage) may also be applied across theferroelectric capacitor 220. In response to the applied voltage, thesubsequent charge Q stored by the ferroelectric capacitor changes, andthe degree of the change may depend on the initial polarization state,the applied voltages, intrinsic or other capacitance on access lines,and other factors. In other words, the charge state or access linevoltage resulting from a read operation may depend on whether the chargestate 305-a, or the charge state 310-a, or some other charge state wasinitially stored, among other factors.

The hysteresis plot 300-a illustrates an example for applying the readvoltage during the activation phase of a read operation to read storedcharge states 305-a and 310-a. A read voltage 315 may be applied, forexample, as a voltage difference via a digit line 210 and a plate line215 as described with reference to FIG. 2. The hysteresis plot 300-a mayillustrate read operations where the read voltage 315 is negativevoltage difference V_(cap) (e.g., where V_(bottom)−V_(plate) isnegative, where V_(DL) is less V_(PL)). A negative read voltage acrossthe ferroelectric capacitor 220 may be referred to as a “plate high”read operation, where a digit line 210 is taken initially to a lowvoltage (e.g., a ground voltage), and a plate line 215 is initially at ahigh voltage. Although the read voltage 315 is shown as a negativevoltage across the ferroelectric capacitor 220, in alternative accessoperations, a read voltage may be a positive voltage across theferroelectric capacitor 220, which may be referred to as a “plate low”read operation.

The read voltage 315 may be applied across the ferroelectric capacitor220 while a memory cell 105 is selected (e.g., by activating a cellselection component 230 via a word line 205 as described with referenceto FIG. 2). Upon applying the read voltage 315 to the ferroelectriccapacitor 220, charge may flow into or out of the ferroelectriccapacitor 220 via the associated digit line 210 and plate line 215, and,in some examples, different charge states or access line voltages mayresult depending on whether the ferroelectric capacitor 220 was at thecharge state 305-a (e.g., storing a logic 0) or at the charge state310-a (e.g., storing a logic 1), or some other charge state.

When performing a read operation on a ferroelectric capacitor 220 at thecharge state 305-a (e.g., a logic 0), the stored charge may reversepolarity as a net negative charge accumulates across the ferroelectriccapacitor 220. In some cases, the read voltage 315 may be reduced (e.g.,compared to a write voltage associated with a greater voltage beingapplied across the memory cell). Here, the reduced read voltage 315 maybe applied across the ferroelectric capacitor 220 and the charge statemay follow the path 320 until reaching the charge and voltage of thecharge state 305-b. Because the reduced read voltage 315 is applied(e.g., instead of a write voltage), the charge state may not follow thepath 320 past charge state 305-b during a first portion of theactivation phase of the read operation. The amount of charge flowingthrough the capacitor 220 may be related to the intrinsic or othercapacitance of the digit line 210 or other access line. In a “platehigh” read configuration, a read operation associated with the chargestates 305-a and 305-b, or more generally a read operation associatedwith the logic 0 state, may be associated with a relatively large amountof charge transfer (e.g., compared to a read operation associated withthe charge states 310-a and 310-b, or more generally the logic 1 state).

When performing the read operation on a ferroelectric capacitor 220 atthe charge state 310-a (e.g., a logic 1), additional negative charge mayaccumulate across the ferroelectric capacitor 220. In some cases, a readvoltage 315 may be applied across the ferroelectric capacitor 220 andthe charge state may follow the path 325 until reaching the charge andvoltage of the charge state 310-b. Because the read voltage 315 isapplied (e.g., instead of a larger write voltage), the charge state 310may not follow the path 325 past charge state 310-b during a firstportion of the activation phase of the read operation. The amount ofcharge flowing through the capacitor 220 may be related to the intrinsicor other capacitance of the digit line 210 or other access line. In a“plate high” read configuration, a read operation associated with thecharge states 310-a and 310-b, or more generally a read operationassociated with the logic 1 state, may be associated with a relativelysmall amount of charge transfer (e.g., compared to a read operationassociated with the charge states 305-a and 305-b, or more generally thelogic 0 state).

The position of the charge state 305-b and the charge state 310-b afterinitiating a read operation may depend on a plurality of factors,including the specific sensing scheme and circuitry. In some cases, thefinal charge may depend on the net capacitance of a digit line 210coupled with the memory cell 105, which may include an intrinsiccapacitance 240, an integrator capacitor (e.g., of a sense component150), and others. For example, if a ferroelectric capacitor 220 iselectrically coupled with a digit line 210 and the read voltage 315 isapplied, the voltage of the digit line 210 may fall when the memory cell105 is selected due to charge flowing from the net capacitance of thedigit line 210 to the ferroelectric capacitor 220. Thus, in someexamples, a voltage measured at a sense component 150 may not be equalto the read voltage 315, and instead may depend on the voltage of thedigit line 210 or other access line following a period of chargesharing.

The initial state (e.g., charge state, logic state) of the ferroelectriccapacitor 220 may be determined by comparing the voltage of a digit line210, or signal line 265 where applicable, resulting from the readoperation with a reference voltage (e.g., via a reference line 285 asdescribed with reference to FIG. 2). In some examples, the digit linevoltage may be the sum of the plate line voltage and the final voltageacross the ferroelectric capacitor 220 (e.g., voltage of charge state305-b when reading the ferroelectric capacitor 220 having a storedcharge state 305-a, or voltage of charge state 310-b when reading theferroelectric capacitor 220 having a stored charge state 310-a).

FIG. 3B may include a hysteresis plot 300-b illustrating the process ofapplying a write voltage 330 to the memory cell during the activationphase of the read operation as well as the refresh and precharge phasesof the read operation. In some cases, the process illustrated by thehysteresis plot 300-b may occur after the process illustrated by thehysteresis plot 300-a.

A logic 0 or 1 may be written to the memory cell 105 by controlling theelectric polarization of the ferroelectric material, and thus the chargeon the capacitor terminals, by applying a net voltage difference acrossthe ferroelectric capacitor 220. For example, after biasing theferroelectric capacitor 220 to either charge state 305-b (e.g., whenreading the ferroelectric capacitor 220 having a stored charge state305-a) or charge state 310-b (e.g., when reading the ferroelectriccapacitor 220 having a stored charge state 310-a) of FIG. 3A, a voltage330 may be applied across the ferroelectric capacitor 220. The voltage330 may correspond to a write voltage 330 and may be greater than theread voltage 315 applied to the memory cell prior to applying the writevoltage 330. Additionally, the voltage 330 may be a voltage equal to orlesser than a negative saturation voltage, and applying the voltage 330across the ferroelectric capacitor 220 may result in charge accumulationuntil the charge state 310-d is reached (e.g., writing a logic 1).

Upon removing the voltage 330 from the ferroelectric capacitor 220(e.g., applying a zero net voltage across the terminals of theferroelectric capacitor 220), the charge state of the ferroelectriccapacitor 220 may follow the path 335 shown between the charge state310-d and the charge state 310-c at zero voltage across the capacitor.In other words, charge state 310-c may represent a logic 1 state at anequalized voltage across a ferroelectric capacitor 220 that has beennegatively saturated.

Similarly, after biasing the ferroelectric capacitor 220 to eithercharge state 305-b or charge state 310-b, a voltage 340 may be appliedacross the ferroelectric capacitor 220 (e.g., during a precharge phaseof the read operation). The voltage 340 may be a voltage equal to orgreater than a positive saturation voltage, and applying the voltage 340across the ferroelectric capacitor 220 may result in charge accumulationuntil the charge state 305-e is reached (e.g., writing a logic 0). Uponremoving the voltage 340 from the ferroelectric capacitor 220 (e.g.,applying a zero net voltage across the terminals of the ferroelectriccapacitor 220), the charge state of the ferroelectric capacitor 220 mayfollow the path 345 shown between the charge state 305-e and the chargestate 305-d at zero voltage across the capacitor. In other words, chargestate 305-d may represent a logic 0 state at an equalized voltage acrossa ferroelectric capacitor 220 that has been positively saturated. Insome examples, the voltage 330 and the voltage 340, representingsaturation voltages, may have the same magnitude, but opposite polarityacross the ferroelectric capacitor 220.

FIG. 4 illustrates a timing diagram 400 that supports memory cellbiasing during a read operation technique in accordance with examples ofthe present disclosure. Timing diagram 400 may illustrate a voltageacross a memory cell (e.g., memory cells 105 as described with referenceto FIGS. 1 through 3) throughout a read operation. The read operationmay include an activation phase 405, a refresh phase 410, and aprecharge phase 415.

Prior to being accessed, the memory cell may be biased to a voltage 425(e.g., V0), which may be approximately equal to 0 volts. Then at T0, thememory cell may be accessed during the activation phase 405 of the readoperation by biasing the cell to the read voltage 430. The read voltage430 may be applied to the memory cell based on a voltage differencebetween the plate line and digit line as described with reference toFIG. 3. Here, the voltage of the digit line may be approximately equalto the read voltage 430 and the voltage of the plate line may beapproximately equal to 0 volts. In some cases, the polarity of the readvoltage may be reversed (e.g., from a positive polarity to a negativepolarity). That is, the voltage of the plate line may be approximatelyequal to the read voltage 430 and the voltage of the digit line may beapproximately equal to 0 volts. Applying the read voltage 430 may causethe charge state of the memory cell may follow the path 320 or 325 basedon a logic state of the memory cell prior to biasing the memory cell tothe read voltage 430 as described with reference to FIG. 3A.

At time T1, the write voltage 435 may be applied to the memory cell.That is, the voltage applied to the memory cell may be increased fromthe read voltage 430 to the write voltage 435. In some cases, the writevoltage 435 may be applied to the memory cell by increasing the voltageof the digit line from approximately equal to the read voltage 430 toapproximately equal to the write voltage 435. In some other cases (e.g.,when the polarity of the voltages applied to the memory cell arereversed), the write voltage 435 may be applied to the memory cell byincreasing the voltage of the plate line from approximately equal to theread voltage 430 to approximately equal to the write voltage 435. Thewrite voltage 435 may correspond to a voltage equal to or greater than asaturation voltage associated with the memory cell. Thus, applying thewrite voltage 435 to the memory cell may cause the charge state of thememory cell to follow the hysteresis curve to a saturation point asdescribed with reference to FIG. 3B. In some cases, this may correspondto programming the memory device to store a logic value ‘1.’

At time T2, the memory cell may be biased to approximately 0 voltsduring the refresh phase 410 of the read operation. The refresh phase410 of the operation may occur after the activation phase 405 and priorto the precharge phase 415 of the read operation. In some cases, therefresh phase 410 of the read operation may be representative of an openpage access operation. In such cases, a duration of the open page accessoperation may extend from the end of the activation phase 405 to thestart of the precharge phase 415 of the read operation.

At time T3, the memory device may initiate a precharge phase 415 of theread operation. During the precharge phase 415 of the read operation,the memory cell may be optionally biased to voltage 425 (e.g., V0) basedon a value stored by the memory cell prior to the read operation. Forexample, if the memory cell was storing a logic value ‘1’ prior to theread operation, the memory device may refrain from applying a prechargepulse. In some other cases, the memory cell may be optionally biased tovoltage 440 (e.g., V1) during the precharge phase 415. For example, ifthe memory cell was storing a logic value ‘0’ prior to the readoperation, the memory device may apply a precharge pulse from time T3 totime T4. In some cases, a magnitude of the voltage 440 (e.g., V1) may beapproximately equal to the write voltage 435 with an opposite polarity.The features of the timing diagram 200 may be used in a memory devicethat uses ferroelectric memory technology. In some cases, the featuresof the timing diagram 200 may be used in other types of memorytechnology, such as random access memory (RAM), read-only memory (ROM),dynamic RAM (DRAM), synchronous dynamic RAM (SDRAM), ferroelectric RAM(FeRAM), magnetic RAM (MRAM), resistive RAM (RRAM), flash memory, phasechange memory (PCM), or others.

FIG. 5 illustrates an example of a circuit 500 that supports memory cellbiasing techniques during a read operation in accordance with examplesas disclosed herein. The circuit 500 includes a sense amplifier 290-afor sensing a logic state of a memory cell 105-b. Electrical charge orother signals may be communicated between the sense amplifier 290-a andthe memory cell 105-b over a digit line 210-a and a signal line 265-a,which may, in combination, be referred to as a single access line of thememory cell 105-b. Signals of the access line may be illustrated byvoltage V_(DL) on the digit line 210-a, and V_(sig) on the signal line265-a, as shown.

The example circuit 500 may include a cascode 505 coupled between thedigit line 210-a and the signal line 265-a, which may be enabled byvoltage source 510-1. In various examples, the cascode 505 may be anexample of a signal development component 260, or otherwise be includedas part of a signal development component 260. The circuit 500 may alsoinclude a word line 205-a for selecting or deselecting the memory cell105-b (e.g., by way of logic signal WL) and a reference line 285-a forproviding a reference signal (e.g., V_(ref), as shown) for comparisonwith a signal of the signal line 265-a when detecting a logic state ofthe memory cell 105-b. The circuit 500 may also include a plate line215-a for accessing a cell plate of a capacitor of the memory cell105-b. Thus, the memory cell 105-b may represent a memory cell 105coupled between a first access line (e.g., the digit line 210-a and thesignal line 265-a) and a second access line (e.g., the plate line215-a).

The circuit 500 may include various voltage sources 510, which may becoupled with various voltage supplies or common grounding or virtualgrounding points of a memory device that includes the example circuit500.

A voltage source 510-a may represent a common grounding point (e.g., achassis ground, a neutral point), which may be associated with a commonreference voltage having a voltage V₀, from which other voltages aredefined. The voltage source 510-a may be coupled with the digit line210-a via the intrinsic capacitance 240-a of the digit line 210-a.

A voltage source 510-b having a voltage V₁ may represent a plate linevoltage source, and may be coupled with the memory cell 105-b via aplate line 215-a of the memory cell 105-b. In some examples, the voltagesource 510-b may be controlled for access operations such as read orwrite operations, including those operations described with reference tohysteresis plots 300-a and 300-b of FIG. 3. In other words, in someexamples, the voltage source 510-b may be a variable voltage source,where a voltage V₁ may have multiple levels.

A voltage source 510-c having a voltage V2 may represent a digit linevoltage source, and may be coupled with the digit line 210-a via aswitching component 520-a, which may be activated or deactivated by alogical signal SW₁.

A voltage source 510-d having a voltage V3 may represent a signal lineprecharge voltage source, and may be coupled with the signal line 265-avia a switching component 520-c, which may be activated or deactivatedby a logical signal SW₃.

A voltage source 510-e having a voltage V4 may represent a referencesignal voltage source, and may be coupled with the reference line 285-avia a switching component 520-f, which may be activated or deactivatedby a logical signal SW₆.

A voltage source 510-1 having a voltage V₁₁ may represent an amplifieror cascode voltage source, and may be coupled with the cascode 505. Insome examples, the cascode 505 may be a transistor or an amplifier, andthe voltage source 510-1 may be coupled with the gate of the transistor.The cascode 505 may be coupled with the signal line 265-a at a firstterminal, and the digit line 210-a at a second terminal. In some cases,a cascode may include two or more transistors coupled in a cascodeconfiguration.

The voltage source 510-1 may be configured to apply various voltages tothe digit line 210-a. That is, the voltage source 510-a may apply avoltage V₁₁ to the gate of the cascode 505. The magnitude of the of thegate voltage applied to the gate of the cascode 505 may affect thevoltage applied to the memory cell. For example, a first magnitude ofthe gate voltage applied to the gate of the cascode 505 may result inthe read voltage (e.g., read pulse) being applied to the memory cell105-b and a second magnitude of the gate voltage applied to the gate ofthe cascode 505 may result in the write voltage (e.g., write pulse)pulse being applied to the memory cell 105-b. If the voltage V₁₁ exceedsthe gate voltage of the cascode 505, a voltage may be applied to thedigit line 210-a (e.g., if the switch 520-b is closed). For example,during an activation phase of a read operation, the voltage source 510-1may apply a voltage equivalent to a sum of the gate voltage of thecascode 505 and the read voltage. Thus, the read voltage may be appliedto the digit line 210-a. After applying the read voltage to the digitline 210-a, the voltage source 510-1 may increase the voltage applied tothe gate of the cascode 505 to a voltage approximately equal to the sumof the gate voltage of the cascode 505 and the write voltage. Here, thewrite voltage may be applied to the digit line 210-a during theactivation phase of the read operation.

When applying a voltage to the digit line 210-a, the voltage across thememory cell 105-b (e.g., the bias voltage applied to the memory cell105-b) may be approximately equal to a difference between the voltage ofthe digit line 210-a and the plate line 215-a. Here, the voltage of theplate line 215-a may be approximately equal to zero volts (e.g., V₁ maybe approximately equal to zero volts) during the activation phase of theread operation. The memory cell 105-b may be biased to the read voltagethen the write voltage during the activation phase based on the voltagesource 510-1 applying voltages to the cascode 505 during the activationphase of the read operation.

The cascode 505 may provide a conversion of charge, voltage, or othersignals between the digit line 210-a and the signal line 265-a. Thecascode 505 may permit a flow of charge (e.g., electrical charge,electrical current) from the signal line 265-a to the digit line 210-a,as fed or enabled by the voltage source 510-1, upon a reduction involtage of the digit line 210-a (e.g., upon selection of the memory cell105-b). Thus, the cascode 505 may be referred to as a charge transfercomponent and may be configured to transfer a charge between the memorycell 105-b and the capacitor 530-a (e.g., associated with the sensecomponent). In some examples, the described flow of charge across thecascode 505 (e.g., from the switch 420-b to the signal line 265-a) maycorrespond to a charge transfer associated with logic states of thememory cell 105-b, or a charge transfer otherwise associated withaccessing the memory cell 105-b. For example, when the memory cell 105-bincludes a ferroelectric capacitor as illustrated by the hysteresisplots 300-a and 300-b, and the cascode 505 is configured to maintain thevoltage of the digit line 210-a to a read voltage (e.g., read voltage315 as described with reference to FIG. 3, read voltage 430 as describedwith reference to FIG. 4), a flow of charge across the cascode 505(e.g., while the memory cell 105-b is biased to the read voltage) maycorrespond to or be otherwise based at least in part on the differencein charge, Q, between charge states 305-b and 305-a when the memory cell105-b stored a logic 0, and a flow of charge across the cascode 505 maycorrespond to or otherwise be based at least in part on the differencein charge, Q, between charge states 310-b and 310-a when the memory cell105-b stored a logic 1.

The circuit 500 may also include a first integrator capacitor 530-a anda second integrator capacitor 530-b, which may each be coupled with arespective variable voltage source 550. For example, the firstintegrator capacitor 530-a may be coupled with the signal line 265-a ata first terminal 531-a, and coupled with a variable voltage source 550-aat a second terminal 532-a. The second integrator capacitor 530-b may becoupled with the reference line 285-a at a first terminal 531-b, andcoupled with a variable voltage source 550-b at a second terminal 532-b

In some examples, a flow of charge across the cascode 505 may beaccompanied by a change in voltage of the signal line 265-a. Forexample, when the signal line 265-a is not otherwise coupled with avoltage source, a relatively small flow of charge to the digit line210-a may be associated with a relatively small change in voltage of thesignal line 265-a, whereas a relatively large flow of charge to thedigit line 210-a may be associated with a relatively large change involtage of the signal line 265-a. Changes in voltage of the signal line265-a associated with an access operation may be based on the netcapacitance of the signal line 265-a (e.g., including the integratorcapacitor 530-a), where the signal line 265-a may undergo a relativelysmall change in voltage or a relatively large change in voltagedepending on the flow of charge across the cascode 505 after selectingthe memory cell 105-b.

In various examples, the cascode 505 may be referred to as a “voltageregulator” or a “bias component,” relating to how the cascode 505regulates a flow of charge in response to the voltage or charge transferof the digit line 210-a. In some examples, the cascode 505, orcombination of the cascode 505 and the integrator capacitor 530-a, maybe referred to as a charge transfer sensing amplifier. The cascode 505may be isolated from the digit line 210-a by a switching component520-b, which may be activated or deactivated by a logical signal SW₂. Insome examples, the switching component 520-b may be part of a columncomponent 135, a multiplexer, or some other circuitry configured toselectively couple the digit line 210-a with the cascode 505 or thesignal line 265-a.

In the example of circuit 500, the variable voltage source 550-a mayinclude a voltage source 510-f having a voltage V5 and a voltage source510-g having a voltage V6, which may be selected for connection with thefirst integrator capacitor 530-a by a switching component 520-d by wayof a logical signal SW₄. In some examples, the voltage source 510-f maybe coupled with a common grounding point (not shown). In other examplesthe voltage source 510-f may be coupled with a voltage supply thatprovides a positive or negative voltage. Voltage source 510-g may becoupled with a voltage supply having a higher voltage than that ofvoltage source 510-f, which may provide a voltage boosting function inaccordance with the difference in voltage between voltage source 510-gand 510-f, equal to V6−V5, or simply V6 when the voltage source 510-f isgrounded.

In the example of circuit 500, the variable voltage source 550-b mayinclude a voltage source 510-h having a voltage V7 and a voltage source510-i having a voltage V₈, which may be selected for connection with thesecond integrator capacitor 530-b by a switching component 520-e by wayof a logical signal SW₅. In some examples, the voltage source 510-h maybe coupled with a common grounding point (not shown). In other examplesthe voltage source 510-h may be coupled with a voltage supply thatprovides a positive or negative voltage. Voltage source 510-i may becoupled with a voltage supply having a higher voltage than that ofvoltage source 510-h, which may provide a voltage boosting function inaccordance with the difference in voltage between voltage source 510-iand 510-h, equal to V₈−V₇, or simply V₈ when the voltage source 510-h isgrounded.

In various examples, one or more components of the circuit 500 may beincluded in or otherwise considered to be part of signal developmentcircuitry, such as a signal development component 260 described withreference to FIG. 2. For example, any one or more of the voltage source510-c, the switching component 520-a, the switching component 520-b, thecascode 505, the voltage source 510-1, the voltage source 510-d, theswitching component 520-c, the variable voltage source 550-a, or theintegrator capacitor 530-a may be included in a signal developmentcomponent 260, or otherwise be considered within the illustrativeboundaries of such a signal development component 260.

Although circuit 500 is shown as including two variable voltage sources550, some configurations in accordance with the present disclosure mayinclude a single, common variable voltage source 550. For example, afirst voltage source 510 of a common variable voltage source 550 may becoupled with both the second terminal 532-a of the first integratorcapacitor 530-a and the second terminal 532-b of the second integratorcapacitor 530-b when a switching component 520 of the common variablevoltage source 550 is deactivated, and a second voltage source 510 ofthe common variable voltage source 550 may be coupled with both thesecond terminal 532-a of the first integrator capacitor 530-a and thesecond terminal 532-b of the second integrator capacitor 530-b when theswitching component 520 of the common variable voltage source 550 isactivated. In some examples that use a common variable voltage source550, the source voltage provided to the second terminal 532-a of thefirst integrator capacitor 530-a may be different to the source voltageprovided to the second terminal 532-b of the second integrator capacitor530-b due to differences in the circuit (e.g., conductor length, width,resistance, capacitance) between the variable voltage source 550 andeach of the integrator capacitors 530.

Further, although the variable voltage sources 550 are illustrated asincluding two voltage sources 510 and a switching component 520, avariable voltage source 550 supporting the operations herein may includeother configurations, such as a voltage buffer that provides a variablevoltage to one or both of the second terminal 532-a of the firstintegrator capacitor 530-a and the second terminal 532-b of the secondintegrator capacitor 530-b. In other examples, a variable voltage source550 may be replaced with fixed voltage sources, or other types ofvoltage sources. Additionally or alternatively, the described operationsof voltage boosting may be omitted from an access operation.

To support various operations described herein, the sense amplifier290-a may be isolated from portions of the circuit 500. For example, thesense amplifier 290-a may be coupled with the signal line 265-a via aswitching component 520-g (e.g., an isolation component, an activationcomponent), which may be activated or deactivated by a logical signalISO′. Additionally or alternatively, the sense amplifier 290-a may becoupled with the reference line 285-a via a switching component 520-h(e.g., an isolation component), which may be activated or deactivated bya logical signal ISO₂. Further, the sense amplifier 290-a may be coupledwith a voltage source 510-j having a voltage V9 and a voltage source510-k having a voltage of V₁₀, which may be examples of sense amplifiervoltage sources 250-b and 250-c, described with reference to FIG. 2,respectively.

Each of the logical signals illustrated in circuit 500 may be providedby a memory controller (not shown), such as a memory controller 170described with reference to FIG. 1. In some examples, certain logicalsignals may be provided by other components. For example, logical signalWL may be provided by a row decoder (not shown), which may be includedin a row component 125 described with reference to FIG. 1.

In various examples, voltage sources 510 may be coupled with differentconfigurations of voltage supplies or common grounding or virtualgrounding points of a memory device that includes the example circuit500. For example, in some examples, voltage sources 510-a, 510-f, 510-h,or 510-j, or any combination thereof, may be coupled with the sameground point or virtual ground point, and may provide substantially thesame reference voltage for various operations of accessing the memorycell 105-b. In some examples, several voltage sources 510 may be coupledwith the same voltage supply of a memory device. For example, in someexamples, voltage sources 510-c, 510-d, 510-g, 510-i, or 510-k, or anycombination thereof, may be coupled with a voltage supply having acertain voltage (e.g., a voltage of 1.5V, which may be referred to as“VARY”). In such examples, the signal line 265-a may be boosted to avoltage substantially equal to 2*VARY, or approximately 3.0V, prior toselecting the memory cell 105-b via word line 205-a for sensing. Inother examples, voltage sources 510-g and 510-i may be coupled with adifferent voltage supply than other voltage supplies (e.g., a voltage of1.2V, which may be referred to as “PDS”), which may thus be associatedwith a voltage boost of 1.2V.

In some examples, the voltage sources 510-j and 510-k may be selectedaccording to particular input/output parameters. For example, voltagesources 510-j and 510-k may be substantially at 0V and 1V, respectively,in accordance with certain input/output component conventions such assome DRAM conventions. Although voltage sources 510 may be coupled withcommon voltage supplies or grounding points, the voltage of each of thevoltage sources 510 coupled with a common voltage supply or commongrounding point may be different due to various differences in thecircuit (e.g., conductor length, width, resistance, capacitance) betweenthe respective voltage sources 510 and the associated common voltagesupply or common grounding point.

Voltage source 510-e may provide a reference voltage for sensing thelogic state of the memory cell 105-b. For example, a voltage of V4 maybe configured to be an average between signal line voltages associatedwith sensing a logic 1 and a logic 0. In some examples, a voltage of V4may be provided as a voltage dropped from a voltage supply of the memorydevice, which may be the same voltage supply coupled with other voltagesources 510. For example, V4 may be provided by connecting voltagesource 510-e with a same voltage supply as voltage source 510-d, butwith an intervening electrical load (e.g., a resistive load orcapacitance) between the voltage supply and the voltage source 510-e).

FIG. 6 illustrates an example of a timing diagram 600 that supportsmemory cell biasing techniques during a read operation in accordancewith examples as disclosed herein. Timing diagram 600 may illustrate anexample read operation including an activation phase 605, a refreshphase 607, and a precharge phase 610. The timing diagram 600 may depictvoltages as a function of time. For example, timing diagram 600 mayinclude a digit line voltage 615, a word line voltage 620, and a plateline voltage 640.

At time T1, the digit line voltage 615 may be charged from 0V to theread voltage 630. For example, as described with reference to FIG. 5, avoltage source (e.g., voltage source 510-1) may apply a voltageapproximately equal to a summation of the read voltage 630 and a gatevoltage of the cascode to charge the digit line to the read voltage 630.At time T2, the word line voltage 620 may be charged from 0V to anactivated word line voltage 620. In such cases, a voltage may be appliedto the word line coupled with the memory cell during read operation. Thememory cell may be accessed based on applying word line voltage 620 tothe word line.

During a first portion of the activation phase 605 (e.g., from time T2to time T3), the signal on the memory cell may develop while the digitline voltage 615 is approximately equal to the read voltage 630, and thedigit line voltage 615, the plate line voltage 640, and the word linevoltage 620 may be maintained at their respective voltages. Here, thememory cell may be biased to the read voltage 630 as the plate linevoltage 640 is approximately equal to 0V. Between time T2 and time T3,charge may be transferred between the memory cell and a capacitorassociated with the sense component (e.g., capacitor 530-a as describedwith reference to FIG. 5). In some cases, the signal may be amplifiedbetween the time T2 and time T3.

In some memory devices, the digit line voltage 615 may be set to thewrite voltage 635 during the first portion of the activation phase 605(e.g., from time T2 to time T3). Here, the memory cell may be biased toapproximately the write voltage 635 and charge may be similarlytransferred between the memory cell and the capacitor associated withthe sense component. In some cases, this may be associated with a lowerdevice reliability (e.g., device lifetime) than memory devices that setthe digit line voltage 615 to the read voltage 630 from time T2 to timeT3. That is, applying the read voltage 630 to the digit line maydecrease the voltage displacement during the read operation whencompared to applying the write voltage 635 to the memory cell from timeT2 to time T3. Additionally, it may desirable to minimize an amount ofvoltage displacement of the memory cell during access operations.Decreasing the voltage displacement during the read operation maydecrease power consumption associated with the read operation anddecrease leakage currents to other memory cells during the readoperation. Additionally, decreasing the digit line voltage 615 from thewrite voltage 635 to the read voltage 630 from time T2 to time T3 maymaintain a read window, thus maintaining a reliability of the readoperation.

At time T3, the digit line voltage 615 may be increased from the readvoltage 630 to the write voltage 635. For example, as described withreference to FIG. 5, a voltage source (e.g., voltage source 510-1) mayapply a voltage approximately equal to a summation of the write voltage635 and a gate voltage of the cascode to charge the digit line to thewrite voltage 635. In some cases, this may program the memory cell to astate (e.g., a logic 0 or a logic 1). In some cases, the sense componentmay be activated at time T3 or after time T3 based on increasing thedigit line voltage 615 to the write voltage 635.

The refresh phase 607 may follow the activation phase 605 from time T4to time T6. At time T4, the memory cell may be programmed to a state.For example, the memory cell may be programmed to a first state or asecond state. If the memory cell is programmed to a first state, thedigit line voltage 615 may decrease at time T5 until time T6 (e.g., asshown by digit line voltage 645). If the memory cell is programmed to asecond state, the digit line voltage 615 may be maintained (e.g., asshown by digit line voltage 650).

At time T6, the precharge phase 610 of the read operation may beinitiated. The digit line voltage 615 may increase as a voltage isapplied to the digit line at time T6. In such cases, the memory cell maybe programmed to the first state.

At time T7, the plate line voltage 640 may increase as a voltage isapplied to the plate line during the precharge phase 610. Here, thememory cell may be biased to a voltage indicated by a difference betweenthe plate line voltage 640 and the digit line voltage 615. In somecases, the polarity of the voltage bias to the memory cell during theprecharge phase 610 may be an opposite polarity as the voltage biasapplied to the memory cell during the activation phase 605.

At time T8, the memory device may begin to resolve the precharge phase610 of the read operation and resolve the read operation at large. Forexample, the plate line voltage 640 may decrease to 0V.

At time T9, the memory device may continue resolving the precharge phase610 by biasing the digit line voltage 615 to voltage 0V.

At time T10, the memory device may resolve and/or complete the readoperation by deactivating the word line voltage 620. Upon biasing theword line voltage, the memory cell may be isolated from the digit line.

FIG. 7 shows a block diagram 700 of a memory device 705 that supportsmemory cell biasing techniques during a read operation in accordancewith examples as disclosed herein. The memory device 705 may be anexample of aspects of a memory device as described with reference toFIGS. 1 through 7. The memory device 705 may include a first voltagebias manager 710, a second voltage bias manager 715, a transfer chargecomponent 720, a sense component manager 725, a precharge component 730,a third voltage bias manager 735, a cascode voltage manager 740, acoupling component 745, a decoupling component 750, and a refresh phasemanager 755. Each of these modules may communicate, directly orindirectly, with one another (e.g., via one or more buses).

The first voltage bias manager 710 may bias a memory cell to a firstvoltage during an activation phase of a read operation. In someexamples, biasing the memory cell to the first voltage may be based on adifference between a third voltage (e.g., applied to a gate of a cascodethat selectively couples a digit line with a sense component) and athreshold voltage of the cascode. In some cases, biasing the memory cellto the first voltage is based on a voltage difference between a digitline and a plate line coupled with the memory cell.

The second voltage bias manager 715 may bias, after biasing the memorycell to the first voltage, the memory cell to a second voltage greaterthan the first voltage during the activation phase of the readoperation. In some cases, biasing the memory cell to the second voltageis based on a voltage difference between the digit line and the plateline coupled with the memory cell. In some instances, biasing the memorycell to the second voltage is based on a difference between a fourthvoltage (e.g., applied to the gate of the cascode that selectivelycouples the digit line with the sense component) and the thresholdvoltage of the cascode.

The transfer charge component 720 may transfer a charge between thememory cell and a capacitor associated with the sense component based onbiasing the memory cell to the first voltage, where biasing the memorycell to the second voltage is based on transferring the charge.

The sense component manager 725 may activate the sense component tostore a value associated with the memory cell based on biasing thememory cell to the second voltage, where initiating the refresh phase ofthe read operation is based on activating the sense component.

The precharge component 730 may initiate, after the refresh phase of theread operation, a precharge phase of the read operation based on a valuestored by the memory cell prior to biasing the memory cell to the firstvoltage.

The third voltage bias manager 735 may bias the memory cell to a thirdvoltage based on initiating the precharge phase of the read operation,where the first voltage and the second voltage have a first polarity andthe third voltage has a second polarity different than the firstpolarity.

The cascode voltage manager 740 may apply the third voltage to the gateof the cascode that selectively couples the digit line with the sensecomponent, where biasing the memory cell to the first voltage is basedon applying the third voltage to the gate of the cascode. In someinstances, the cascode voltage manager 740 may apply the fourth voltagegreater than the third voltage to the gate of the cascode, where biasingthe memory cell to the second voltage is based at least in part onapplying the fourth voltage to the gate of the cascode.

The coupling component 745 may couple the memory cell with the digitline after applying the third voltage to the cascode, where biasing thememory cell to the first voltage during the activation phase of the readoperation is based on coupling the memory cell with the digit line.

The decoupling component 750 may decouple the memory cell from the digitline after initiating a precharge phase of the read operation.

The refresh phase manager 755 may initiate a refresh phase of the readoperation based on biasing the memory cell to the second voltage. Insome examples, the refresh phase manager 755 may maintain the memorycell at the second voltage during the refresh phase of the readoperation based on a first value being stored by the memory cell priorto biasing the memory cell to the first voltage. Additionally oralternatively, the refresh phase manager 755 may decrease, from thesecond voltage, a bias applied to the memory cell during the refreshphase of the read operation based on a second value being stored by thememory cell prior to biasing the memory cell to the first voltage.

FIG. 8 shows a flowchart illustrating a method or methods 800 thatsupports memory cell biasing techniques during a read operation inaccordance with examples as disclosed herein. The operations of method800 may be implemented by a memory device or its components as describedherein. For example, the operations of method 800 may be performed by amemory device as described with reference to FIG. 7. In some examples, amemory device may execute a set of instructions to control thefunctional elements of the memory device to perform the describedfunctions. Additionally or alternatively, a memory device may performaspects of the described functions using special-purpose hardware.

At 805, the memory device may bias a memory cell to a first voltageduring an activation phase of a read operation. The operations of 805may be performed according to the methods described herein. In someexamples, aspects of the operations of 805 may be performed by a firstvoltage bias manager as described with reference to FIG. 7.

At 810, the memory device may bias, after biasing the memory cell to thefirst voltage, the memory cell to a second voltage greater than thefirst voltage during the activation phase of the read operation. Theoperations of 810 may be performed according to the methods describedherein. In some examples, aspects of the operations of 810 may beperformed by a second voltage bias manager as described with referenceto FIG. 7.

At 815, the memory device may initiate a refresh phase of the readoperation based on biasing the memory cell to the second voltage. Theoperations of 815 may be performed according to the methods describedherein. In some examples, aspects of the operations of 815 may beperformed by a refresh phase manager as described with reference to FIG.7.

In some examples, an apparatus as described herein may perform a methodor methods, such as the method 800. The apparatus may include features,means, or instructions (e.g., a non-transitory computer-readable mediumstoring instructions executable by a processor) for biasing a memorycell to a first voltage during an activation phase of a read operation,biasing, after biasing the memory cell to the first voltage, the memorycell to a second voltage greater than the first voltage during theactivation phase of the read operation, and initiating a refresh phaseof the read operation based on biasing the memory cell to the secondvoltage.

Some cases of the method 800 and the apparatus described herein mayfurther include operations, features, means, or instructions fortransferring a charge between the memory cell and a capacitor associatedwith a sense component based on biasing the memory cell to the firstvoltage, where biasing the memory cell to the second voltage may bebased on transferring the charge.

Some instances of the method 800 and the apparatus described herein mayfurther include operations, features, means, or instructions foractivating a sense component to store a value associated with the memorycell based on biasing the memory cell to the second voltage, whereinitiating the refresh phase of the read operation may be based onactivating the sense component.

Some examples of the method 800 and the apparatus described herein mayfurther include operations, features, means, or instructions forinitiating, after the refresh phase of the read operation, a prechargephase of the read operation based on a value stored by the memory cellprior to biasing the memory cell to the first voltage.

Some cases of the method 800 and the apparatus described herein mayfurther include operations, features, means, or instructions for biasingthe memory cell to a third voltage based on initiating the prechargephase of the read operation, where the first voltage and the secondvoltage may have a first polarity and the third voltage may have asecond polarity different than the first polarity.

Some instances of the method 800 and the apparatus described herein mayfurther include operations, features, means, or instructions forapplying a third voltage to a gate of a cascode that selectively couplesa digit line with a sense component, where biasing the memory cell tothe first voltage may be based on applying the third voltage to the gateof the cascode, and applying a fourth voltage greater than the thirdvoltage to the gate of the cascode, where biasing the memory cell to thesecond voltage may be based at least in part on applying the fourthvoltage to the gate of the cascode.

In some examples of the method 800 and the apparatus described herein,biasing the memory cell to the first voltage may be based at least on adifference between the third voltage and a threshold voltage of thecascode, and biasing the memory cell to the second voltage may be basedon a difference between the fourth voltage and the threshold voltage ofthe cascode.

Some cases of the method 800 and the apparatus described herein mayfurther include operations, features, means, or instructions forcoupling the memory cell with the digit line after applying the thirdvoltage to the cascode, where biasing the memory cell to the firstvoltage during the activation phase of the read operation may be basedon coupling the memory cell with the digit line.

Some instances of the method 800 and the apparatus described herein mayfurther include operations, features, means, or instructions fordecoupling the memory cell from the digit line after initiating aprecharge phase of the read operation.

Some examples of the method 800 and the apparatus described herein mayfurther include operations, features, means, or instructions formaintaining the memory cell at the second voltage during the refreshphase of the read operation based on a first value being stored by thememory cell prior to biasing the memory cell to the first voltage; ordecreasing, from the second voltage, a bias applied to the memory cellduring the refresh phase of the read operation based on a second valuebeing stored by the memory cell prior to biasing the memory cell to thefirst voltage.

In some cases of the method 800 and the apparatus described herein,biasing the memory cell to the first voltage and the second voltage maybe based on a voltage difference between a digit line and a plate linecoupled with the memory cell.

It should be noted that the methods described herein are possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Furthermore, portions from two or more of the methods may be combined.

An apparatus is described. The apparatus may include a biasing componentconfigured to bias a memory cell to a first voltage during an activationphase of a read operation, and bias, after biasing the memory cell tothe first voltage, the memory cell to a second voltage greater than thefirst voltage during the activation phase of the read operation. Theapparatus may further include a refresh component for initiating arefresh phase of the read operation based on biasing the memory cell tothe second voltage.

Some examples of the apparatus may include a charge transfer componentfor transferring a charge between the memory cell and a capacitorassociated with a sense component based on biasing the memory cell tothe first voltage, where biasing the memory cell to the second voltagemay be based on transferring the charge.

Some cases of the apparatus may include an activation component foractivating a sense component to store a value associated with the memorycell based on biasing the memory cell to the second voltage, whereinitiating the refresh phase of the read operation may be based onactivating the sense component.

Some instances of the apparatus may include a precharge component forinitiating, after the refresh phase of the read operation, a prechargephase of the read operation based on a value stored by the memory cellprior to biasing the memory cell to the first voltage.

In some examples, the biasing component may be further configured tobias the memory cell to a third voltage based on initiating theprecharge phase of the read operation, where the first voltage and thesecond voltage may have a first polarity and the third voltage may havea second polarity different than the first polarity.

In some cases, the biasing component may be further configured to applya third voltage to a gate of a cascode that selectively couples a digitline with a sense component, where biasing the memory cell to the firstvoltage may be based on applying the third voltage to the gate of thecascode, and apply a fourth voltage greater than the third voltage tothe gate of the cascode, where biasing the memory cell to the secondvoltage may be based on applying the fourth voltage to the gate of thecascode.

In some instances, biasing the memory cell to the first voltage may bebased at least on a difference between the third voltage and a thresholdvoltage of the cascode, and biasing the memory cell to the secondvoltage may be based on a difference between the fourth voltage and thethreshold voltage of the cascode.

Some examples of the apparatus may include a coupling componentconfigured to couple the memory cell with the digit line after applyingthe third voltage to the cascode, where biasing the memory cell to thefirst voltage during the activation phase of the read operation may bebased on coupling the memory cell with the digit line.

In some cases, the coupling component may be further configured todecouple the memory cell from the digit line after initiating aprecharge phase of the read operation.

In some instances, the biasing component may be further configured tomaintain the memory cell at the second voltage during the refresh phaseof the read operation based on a first value being stored by the memorycell prior to biasing the memory cell to the first voltage; or decrease,from the second voltage, a bias applied to the memory cell during therefresh phase of the read operation based on a second value being storedby the memory cell prior to biasing the memory cell to the firstvoltage.

In some examples, biasing the memory cell to the first voltage and thesecond voltage may be based on a voltage difference between a digit lineand a plate line coupled with the memory cell.

An apparatus is described. The apparatus may include a memory array anda controller coupled with the memory array and operable to bias a memorycell of the memory array to a first voltage during an activation phaseof a read operation, bias, after biasing the memory cell to the firstvoltage, the memory cell to a second voltage greater than the firstvoltage during the activation phase of the read operation, and initiatea refresh phase of the read operation based on biasing the memory cellto the second voltage.

In some examples, the controller may be further operable to transfer acharge between the memory cell and a capacitor associated with a sensecomponent based on biasing the memory cell to the first voltage, wherebiasing the memory cell to the second voltage may be based ontransferring the charge.

In some cases, the controller may be further operable to activate asense component to store a value associated with the memory cell basedon biasing the memory cell to the second voltage, where initiating therefresh phase of the read operation may be based on activating the sensecomponent.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof. Some drawings may illustrate signals as a single signal;however, it will be understood by a person of ordinary skill in the artthat the signal may represent a bus of signals, where the bus may have avariety of bit widths.

The terms “electronic communication,” “conductive contact,” “connected,”and “coupled” may refer to a relationship between components thatsupports the flow of signals between the components. Components areconsidered in electronic communication with (or in conductive contactwith or connected with or coupled with) one another if there is anyconductive path between the components that can, at any time, supportthe flow of signals between the components. At any given time, theconductive path between components that are in electronic communicationwith each other (or in conductive contact with or connected with orcoupled with) may be an open circuit or a closed circuit based on theoperation of the device that includes the connected components. Theconductive path between connected components may be a direct conductivepath between the components or the conductive path between connectedcomponents may be an indirect conductive path that may includeintermediate components, such as switches, transistors, or othercomponents. In some examples, the flow of signals between the connectedcomponents may be interrupted for a time, for example, using one or moreintermediate components such as switches or transistors.

The term “coupling” refers to condition of moving from an open-circuitrelationship between components in which signals are not presentlycapable of being communicated between the components over a conductivepath to a closed-circuit relationship between components in whichsignals can be communicated between components over the conductive path.When a component, such as a controller, couples other componentstogether, the component initiates a change that allows signals to flowbetween the other components over a conductive path that previously didnot permit signals to flow.

The term “isolated” refers to a relationship between components in whichsignals are not presently capable of flowing between the components.Components are isolated from each other if there is an open circuitbetween them. For example, two components separated by a switch that ispositioned between the components are isolated from each other when theswitch is open. When a controller isolates two components from oneanother, the controller affects a change that prevents signals fromflowing between the components using a conductive path that previouslypermitted signals to flow.

As used herein, the term “substantially” means that the modifiedcharacteristic (e.g., a verb or adjective modified by the termsubstantially) need not be absolute but is close enough to achieve theadvantages of the characteristic.

The devices discussed herein, including a memory array, may be formed ona semiconductor substrate, such as silicon, germanium, silicon-germaniumalloy, gallium arsenide, gallium nitride, etc. In some examples, thesubstrate is a semiconductor wafer. In other cases, the substrate may bea silicon-on-insulator (SOI) substrate, such as silicon-on-glass (SOG)or silicon-on-sapphire (SOS), or epitaxial layers of semiconductormaterials on another substrate. The conductivity of the substrate, orsub-regions of the substrate, may be controlled through doping usingvarious chemical species including, but not limited to, phosphorous,boron, or arsenic. Doping may be performed during the initial formationor growth of the substrate, by ion-implantation, or by any other dopingmeans.

A switching component or a transistor discussed herein may represent afield-effect transistor (FET) and comprise a three terminal deviceincluding a source, drain, and gate. The terminals may be connected toother electronic elements through conductive materials, e.g., metals.The source and drain may be conductive and may comprise a heavily-doped,e.g., degenerate, semiconductor region. The source and drain may beseparated by a lightly-doped semiconductor region or channel. If thechannel is n-type (i.e., majority carriers are electrons), then the FETmay be referred to as a n-type FET. If the channel is p-type (i.e.,majority carriers are holes), then the FET may be referred to as ap-type FET. The channel may be capped by an insulating gate oxide. Thechannel conductivity may be controlled by applying a voltage to thegate. For example, applying a positive voltage or negative voltage to ann-type FET or a p-type FET, respectively, may result in the channelbecoming conductive. A transistor may be “on” or “activated” when avoltage greater than or equal to the transistor's threshold voltage isapplied to the transistor gate. The transistor may be “off” or“deactivated” when a voltage less than the transistor's thresholdvoltage is applied to the transistor gate.

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details toproviding an understanding of the described techniques. Thesetechniques, however, may be practiced without these specific details. Insome instances, well-known structures and devices are shown in blockdiagram form to avoid obscuring the concepts of the described examples.

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), anapplication-specific integrated circuit (ASIC), a field programmablegate array (FPGA) or other programmable logic device, discrete gate ortransistor logic, discrete hardware components, or any combinationthereof designed to perform the functions described herein. Ageneral-purpose processor may be a microprocessor, but in thealternative, the processor may be any processor, controller,microcontroller, or state machine. A processor may also be implementedas a combination of computing devices (e.g., a combination of a DSP anda microprocessor, multiple microprocessors, one or more microprocessorsin conjunction with a DSP core, or any other such configuration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations.

Also, as used herein, including in the claims, “or” as used in a list ofitems (for example, a list of items prefaced by a phrase such as “atleast one of” or “one or more of”) indicates an inclusive list suchthat, for example, a list of at least one of A, B, or C means A or B orC or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein,the phrase “based on” shall not be construed as a reference to a closedset of conditions. For example, an exemplary step that is described as“based on condition A” may be based on both a condition A and acondition B without departing from the scope of the present disclosure.In other words, as used herein, the phrase “based on” shall be construedin the same manner as the phrase “based at least in part on.”

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be apparent to those skilled in the art, and the generic principlesdefined herein may be applied to other variations without departing fromthe scope of the disclosure. Thus, the disclosure is not limited to theexamples and designs described herein but is to be accorded the broadestscope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. An apparatus, comprising: a biasing componentconfigured to: apply a first voltage to a digit line of a memory cellduring a first phase of an access operation; increase the first voltageto a second voltage during the first phase of the access operation;maintain a third voltage at a plate line of the memory cell for aduration based at least in part on increasing the first voltage to thesecond voltage; and initiate a second phase of the access operationbased at least in part on a voltage difference between the secondvoltage and the third voltage.
 2. The apparatus of claim 1, furthercomprising: a charge transfer component for transferring a chargebetween the memory cell and a capacitor associated with a sensecomponent based at least in part on a second difference between thefirst voltage and the third voltage, wherein the biasing component isconfigured to increase the first voltage to the second voltage based atleast in part on transferring the charge.
 3. The apparatus of claim 1,further comprising: an activation component for activating a sensecomponent to store a value associated with the memory cell based atleast in part on increasing the first voltage to the second voltage,wherein the biasing component is configured to initiate the second phaseof the access operation based at least in part on activating the sensecomponent.
 4. The apparatus of claim 1, further comprising: a prechargecomponent for initiating, after the second phase of the accessoperation, a third phase of the access operation based at least in parton a value stored by the memory cell prior to increasing the firstvoltage to the second voltage.
 5. The apparatus of claim 1, wherein thebiasing component is further configured to: apply a fourth voltage to agate of a cascode that selectively couples the digit line with a sensecomponent, wherein applying the first voltage to the digit line is basedat least in part on applying the fourth voltage to the gate of thecascode; and apply a fifth voltage greater than the fourth voltage tothe gate of the cascode, wherein the biasing component is configured toincrease the first voltage to the second voltage based at least in parton applying the fifth voltage to the gate of the cascode.
 6. Theapparatus of claim 5, wherein: applying the first voltage to the digitline is based at least on a difference between the fourth voltage and athreshold voltage of the cascode; and increasing the first voltage tothe second voltage is based at least in part on a difference between thefifth voltage and the threshold voltage of the cascode.
 7. The apparatusof claim 5, further comprising: a coupling component configured tocouple the memory cell with the digit line after applying the fourthvoltage to the cascode, wherein the biasing component is configured toapply the first voltage to the digit line based at least in part oncoupling the memory cell with the digit line.
 8. The apparatus of claim7, wherein the coupling component is further configured to: decouple thememory cell from the digit line after initiating a third phase of theaccess operation.
 9. The apparatus of claim 1, wherein the biasingcomponent is further configured to: maintain the digit line at thesecond voltage during the second phase of the access operation based atleast in part on a first value being stored by the memory cell prior toapplying the first voltage to the digit line; or decrease, from thesecond voltage, during the second phase of the access operation based atleast in part on a second value being stored by the memory cell prior toapplying the first voltage to the digit line.
 10. A method, comprising:applying a first voltage to a digit line of a memory cell during a firstphase of an access operation; increasing the first voltage to a secondvoltage during the first phase of the access operation; maintaining athird voltage at a plate line of the memory cell for a duration based atleast in part on increasing the first voltage to the second voltage; andinitiating a second phase of the access operation based at least in parton a voltage difference between the second voltage and the thirdvoltage.
 11. The method of claim 10, further comprising: transferring acharge between the memory cell and a capacitor associated with a sensecomponent based at least in part on a second difference between thefirst voltage and the third voltage, wherein increasing the firstvoltage to the second voltage is based at least in part on transferringthe charge.
 12. The method of claim 10, further comprising: activating asense component to store a value associated with the memory cell basedat least in part on increasing the first voltage to the second voltage,wherein initiating the second phase of the access operation is based atleast in part on activating the sense component.
 13. The method of claim10, further comprising: initiating, after the second phase of the accessoperation, a third phase of the access operation based at least in parton a value stored by the memory cell prior to increasing the firstvoltage to the second voltage.
 14. The method of claim 10, furthercomprising: applying a fourth voltage to a gate of a cascode thatselectively couples the digit line with a sense component, whereinapplying the first voltage to the digit line is based at least in parton applying the fourth voltage to the gate of the cascode; and applyinga fifth voltage greater than the fourth voltage to the gate of thecascode, wherein increasing the first voltage to the second voltage isbased at least in part on applying the fifth voltage to the gate of thecascode.
 15. The method of claim 14, wherein: applying the first voltageto the digit line is based at least on a difference between the fourthvoltage and a threshold voltage of the cascode; and increasing the firstvoltage to the second voltage is based at least in part on a differencebetween the fifth voltage and the threshold voltage of the cascode. 16.The method of claim 14, further comprising: coupling the memory cellwith the digit line after applying the fourth voltage to the cascode,wherein applying the first voltage to the digit line is based at leastin part on coupling the memory cell with the digit line.
 17. The methodof claim 16, further comprising: decoupling the memory cell from thedigit line after initiating a third phase of the access operation. 18.The method of claim 10, further comprising: maintaining the digit lineat the second voltage during the second phase of the access operationbased at least in part on a first value being stored by the memory cellprior to applying the first voltage to the digit line; or decreasing,from the second voltage, during the second phase of the access operationbased at least in part on a second value being stored by the memory cellprior to applying the first voltage to the digit line.
 19. The method ofclaim 10, further comprising: increasing the first voltage to the secondvoltage is based at least in part on a voltage difference between thedigit line and the plate line.
 20. An apparatus, comprising: a memoryarray; and a controller coupled with the memory array and operable to:apply a first voltage to a digit line of a memory cell during a firstphase of an access operation; increase the first voltage to a secondvoltage during the first phase of the access operation; maintain a thirdvoltage at a plate line of the memory cell for a duration based at leastin part on increasing the first voltage to the second voltage; andinitiate a second phase of the access operation based at least in parton a voltage difference between the second voltage and the thirdvoltage.